Proper navigation of an aircraft in all phases of flight is based primarily on an ability to identify any terrain features over which the aircraft is passing, and further based on the ability to determine a position of the aircraft. In this regard, aircraft instrumentation, including navigational sensors, radar systems, and specifically, radar altimeters are used in combination with accurate electronic terrain maps. The electronic terrain maps provide the height of objects on the map, and together with the radar altimeter aid in the flight and the planning of a flight path for the aircraft. As such, radar altimeters are commonly implemented within aircraft.
The typical aircraft radar altimeter includes a transmitter for applying pulses of electromagnetic energy at regular intervals to an antenna which then radiates the energy, in the form of a transmit beam, towards the Earth's surface. The radar altimeter further includes a signal receiver which receives return pulses, sometimes referred to as an echo or a return signal. For example, the return pulses that are received at an antenna receiver of the radar altimeter constitute radar transmission beams that have been reflected from the Earth's surface.
Military aircraft will frequently fly at very low altitudes to avoid detection. Flying at these very low altitudes dramatically increases a probability that the aircraft will collide with terrain objects (for example, buildings, mountains, or the side of a cliff). Standard aircraft radar altimeters that are designed to provide vertical altitude are largely incapable of detecting objects that are in a forward range of a known or desired flight path. Moreover, the electronic terrain maps often lack adequate resolution for safe flight at very low altitudes and are updated so infrequently that any obstacle less than 30 days old is unlikely to appear on the map.
In addition, emerging communications standards have made available a wealth of information that is of value to a pilot. This is particularly so for military pilots where delays in receiving information often means lost opportunities or casualties. For known applications where radar altimeters are utilized, radar functions and datalink communications functions are performed by separate transmitting and receiving devices, if the datalink function is available at all. While radars and datalink communications equipment incorporate separate transmitting and receiving devices, they are typically operated in separate frequency bands, each including separate antenna systems. Typically, space is at a premium for very small aircraft and even more so for helicopters. Since a radar altimeter is a mandatory item for any military aircraft and many civilian aircraft, the additional space required for a datalink transceiver typically rules out having the datalink receiver onboard.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a radar altimeter with forward looking radar and data transfer capabilities.